At first, I thought that you wanted to parse an HTML file as an input, to get information out of it. For that purpose, I would have suggested that you search for "html parse" at http://search.cpan.org.

But instead I think that you may want to generate a customized HTML content using the file shown above as a template. There are numerous templating engines available in Perl. My personal favorite happens to be Template::Toolkit. Although it is most often used in interactive web-sites, it can be used very well in situations like this, especially when you would like to vary what is produced, e.g.: "Thank you for your payment! :-)"vs."Pay Up Now, You Scum, Or Your Parakeet Gets It! :-[" depending on the balance.

Start with this tutorial, which deals specifically with how to generate a file (or a string) from a templated source: Template::Tutorial::Datafile.